The present invention relates to an accessory for an air circuit breaker. An accessory is typically designed to fit onto a latching shaft included in the circuit breaker. The accessory is often used to provide communication between a latching shaft and an actuation device within the circuit breaker.
Air circuit breakers are commonly used in electrical distribution systems. A typical air circuit breaker comprises a component for connecting an electrical power source to electrical power consumer called a load. The component is referred to as a main contact assembly. A main contact is typically either opened, interrupting a path for power to travel from the source to the load, or closed, providing a path for power to travel from the source to the load. In many air circuit breakers, the force necessary to open or close the main contact assembly is provided by an arrangement of compression springs. When the compression springs discharge, they exert a force that provides the energy needed to open or close the main contacts. Compression springs that provide a force to close the main contacts are often called closing springs. Compression springs that provide a force to open the main contacts are often referred to as contact springs.
In many air circuit breakers, the mechanism for controlling the compression springs comprises a configuration of mechanical linkages between a latching shaft and an actuation device. The actuation device may be manually or electrically operated. An electrically operated actuation device generally operates when a particular electrical condition is sensed, for example, under voltage or remote operation of breaker for closing and opening conditions. The actuation device within the circuit breaker typically imparts a force onto an accessory. The accessory then translates the force from the actuation device into a rotational force exerted on the latching shaft. The latching shaft then rotates. This rotation is translated through the mechanical linkages to unlatch or activate either the closing springs or the contact springs. There is typically a first latching shaft mechanically linked to the closing springs called the closing shaft. A second latching shaft is mechanically linked to the contact springs called the tripping shaft.
As each actuation device acts upon the latching shaft via a corresponding accessory, the accessory acts as a lever converting a linear force from the actuation device to a rotational force on the latching shaft. The accessory is disposed in contact with the latching shaft and attached to the latching shaft by a fixing mechanism. A common fixing mechanism typically includes a threaded fastener, a rivet joint or a pin assembly. Additionally, the fixing mechanism is normally metallic. Thus, a typical fixing mechanism requires selective local heat treatment of the latching shaft, tapping of the latching shaft and the accessory, riveting, or a pin assembly. These processes add to the cost and time of production. Additionally, the fixing mechanism tends to loosen over time.
Thus, it is desirable to reduce the time and cost of production by developing a fixing mechanism that eliminates metallic threaded fasteners, rivet joints and pin assemblies. Eliminating metallic threaded fasteners, rivet joints and pin assembly fixing mechanisms may also prevent loosening of fixing mechanisms over time.